I don't know that area well, but from what you're describing, I would say to go with more tread than something like the SM8. It's more of a flat, hardpack dirt, xc-ish tire. Something like that isn't going to be that great on loose, rocky, or sandy stuff. See if you can find a MTB group website in your area and search their site for tire info. And just in case you haven't found it, there's always a search feature at the top, right corner of the thread list in each subforum. That way you can just search for tires and don't have to page through tons of unrelated stuff. Learning to use the exact search terms can take some practice, though.

EDIT: I bet if you join this forum and introduce yourself, they can help you out with the local MTB questions like what tires are good in the area. Maybe even find some riding buddies. http://www.socaltrailriders.org/forum/